1. Technical Field
The present invention relates to a damper apparatus configured to open and close an ink channel connecting an ink tank and a printer head, a damper tube assembly, and an ink jet printer.
2. Description of the Related Art
An ink jet printer is an apparatus configured to draw information such as characters, graphics, patterns, images on a surface of an object to be printed by discharging ink droplets on a printing medium from nozzles of a printer head while moving the printer head formed generally with a number of nozzles reciprocally with respect to the printing medium. In the ink jet printer in this configuration, for example, a cartridge-type ink tank is mounted on the side of a printer body, and ink stored in the ink tank is supplied to a printer head via a flexible ink tube. When the printer head moves reciprocally with respect to the printing medium for a printing operation, part of the ink tube connected to the printer head (the downstream side of the ink tube) is moved at the same velocity as the printer head. Therefore, in the reciprocal motion of the printer head, in accelerating and decelerating areas where the direction of movement is inverted, an inertial force in the direction of travel or in the direction opposite therefrom acts on the ink itself accumulated in the ink tube. When the inertial force causes the pressure in the ink tube to vary according to the self-weight of the ink and the internal pressure of the head is significantly pressurized, “dripping” of ink, that is, ejection of large ink drop from a nozzle of the printer head occurs. In contrast, when the internal pressure of the printer head is significantly reduced, a meniscus formed in the nozzle is broken, and an air bubble is sucked into the printer head, which may cause an ink undischarged phenomenon that the discharge of ink is disabled (also referred to as “nozzle skip”) may occur. Accordingly, in order to inhibit the pressure variations in the printer head, various types of damper apparatuses to be provided at a midpoint of the ink tube are proposed and put into practical application in the related art (for example, see JP-A-11-20144).
The damper apparatus of the related art includes a rectangular box-shaped housing communicating with the ink tube and opening at one end surface thereof, and a flexible damper film configured to cover an opening surface of the housing, so that the damper film is deflected outward or inward according to the pressure variations of the ink, thereby changing the capacity of the damper chamber formed in the interior of the housing and absorbing the pressure variation. However, the damper apparatus of this type has a problem in that the damping function (pressure inhibiting function) varies depending on an initial state of the damper chamber. For example, even though the ink pressure acts on the pressurizing side when the damper film is deflected outward and the damper chamber is expanded to the maximum, the capacity in the damper chamber is not increased any longer, and hence the damping function does not work. In contrast, even though the ink pressure acts on the depressurizing side when the damper film is deflected inward and the damper chamber is in the contracted state, the capacity of the damper chamber is not reduced any longer, and hence the damping function does not work as well in this case as well. As described above, in the damper apparatus having the configuration of the related art, when the carriage is accelerated and decelerated in association with the reciprocal motion thereof, and the ink pressure variations occur in the pressurizing or depressurizing direction in the printer head correspondingly, the damping function may not work sufficiently.